Raise your left knee towards your right shoulder as you rotate your hips to up and to the right as far as you can. Then reverse directions, rotating your hips up and to the left, and try to touch your right foot to the back of your left shoulder (you won’t be able to do it). That’s one repetition.

After you’ve finished all of your repetitions (130 seconds) with your left leg, repeat with your right leg. To make it harder, do the exercise with your shins on a Swiss-ball (instead of putting your feet on the bench).